1. Technical Field
The present invention relates to a flat type vibration motor.
2. Description of the Related Art
In portable electronic apparatuses such as a cellular phone, a game machine, a portable information terminal, etc., various types of vibration generation devices are mounted on the portable electronic apparatuses in order to prevent disturbing other people due to sound. In particular, the vibration generation device is mounted in the cellular phone sp as to be used as a silent receiving signal generating device and with miniaturization and slimming tendencies of the cellular phones, vibration generating devices mounted therein also require miniaturization and high functionality.
The vibration generating devices use various types of vibration motors as vibration sources. A general vibration motor is separately fixed to a cellular phone set, and the like and connected to a PCB of the cellular phone set through soldering by using a lead wire. However, the vibration motor needs a manual work in a process of fixing the vibration motor to the cellular phone set and a process of soldering the lead wire.
In order to solve the problems, a surface mounted device (SMD) type vibration motor surface-mounted onto and soldered to the PCB of the cellular phone set is being used.
FIG. 1 is a cross-sectional view of an SMD type vibration motor in the prior art and a problem in the prior art will be described with reference to FIG. 1.
As shown in FIG. 1, the SMD type vibration motor 10 in the prior art includes a bracket 12 to which a printed circuit board 11 is fixed, a case 13 partitioning an internal space while covering the top of the bracket 12, a shaft 14 supported by the bracket 12, a magnet which is a stator 15 installed on the top of the bracket 12, and a rotor 16 eccentrically installed in the shaft 14 to be rotatable.
Herein, the rotor 16 includes an upper substrate 16a with a commutator 16b formed on the bottom thereof, a bearing 16c rotatably supported on the shaft 14, a coil 16d and a weight body 16e provided on the top of the upper substrate 16a, and a molding member 16f integrally connecting the upper substrate 16a, the coil 16d, and the weight body 16e to each other.
Further, one portion of a brush 17 is connected to the printed circuit board 11 through welding. The other portion of the brush 17 is connected to the commutator 16b to transmit external power to the coil 16d. 
The SMD type vibration motor 10 adopting the structure generates vibration while the rotor 16 rotates by electromagnetic force formed between the coil 16d and the stator 15 when the external power is supplied to the coil 16d by passing through the printed circuit board 11, the brush 17, and the commutator 16b in sequence.
However, in the SMD type vibration motor 10 in the prior art, since the bracket 12 is fixed to the printed circuit board 11 by using a double-sided adhesive tape or a bond, the bracket 12 is not solidly fixed to the printed circuit board 11 and as a result, rotational vibration force of the rotor 16 is decreased or the bracket 12 is separated from the printed circuit board 11 due to the rotation vibration force.
Further, the SMD type vibration motor 10 in the prior art does not include any component that can reduce electromagnetic wave noise generated during the rotation of the motor.
Moreover, since the motor is fixed to the PCB of the cellular phone set by soldering only an external power connection terminal of the printed circuit board 11, fixation force is weak and as a result, when vibration is generated or an impact is received, the motor may be separated from the PCB and the vibration force generated from the rotor 16 cannot be securely transmitted to the cellular phone set.